Hello,It depends where "here" is. If you're American, the exchange rates are horrible - buy your yen in Japan. But the best way, as said, is really through your ATM card at a Japanese 7-11 or post office.

We took a lot of yen last year ordered from the bank .We had a lot left over as we used credit card in many places .This year we ran out 3rd week sadly Brexit occured that week and got terrible rate in bank Tokyo .